Electric motor control system



Nov. 19, 1935. LOCK-ETT 2,021,239

ELECTRIC MOTOR CONTROL SYSTEM Filed Feb'. 1, 1955 Patented Nov. 19, 1935 PATENT OFFICE ELECTRIC MOTOR CONTROL SYSTEM Ralph G. Lockett, Wauwatosa, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, '15., a corporation of Delaware Application February 1, 1935, Serial No.

8 Claims.

This invention relates to improvements in. electric motor control systems. Although not limited thereto, the invention is particularly applicable to control of the fan and cylinder driving motors of a clothes-drying tumbler or the like.

An object of the invention is to provide a novel system of control for a plurality of associated electric driving motors.

Another object is to provide a system of the character aforementioned wherein a single manual control instrumentality may be utilized to initiate joint operation of the motors.

Another object is to provide such a system wherein a single manual control instrumentality may be utilized to simultaneously interrupt the energizing circuits of both motors.

Another object is to provide a system of the aforementioned character embodying a relatively large motor and a relatively small motor, and

wherein the starting resistance for the relatively large motor is utilized to additionally provide initial protection for the relatively small motor during starting.

Another and more specific object is to provide a simple form of starting control means for a relatively large fan operating motor, said means being utilized to insure protection to a relatively small cylinder driving motor having a reversing and accelerating control drum and resistance sections individual thereto.

Another object is to provide a system wherei the fan motor is utilized to drive the reversing and accelerating control drum associated with the cylinder motor. 7

Another object is to generally improve and simplify the control means for a plurality of associated driving motors to provide for accomplishment of the novel results aforementioned.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates an embodiment of the invention which will now be described, it being understood that the embodiment illustrated is susceptible of modification without departing from the scope of the appended claims.

The drawing illustrates schematically and di- I agrammatically a, system of control for the relatively large fan driving motor and for the relatively small cylinder driving motor of a clothesdrying tumbler of the character employed in laundering establishments.

Referring to the drawing, the numeral designates the rotatable cylinder of a well known form of clothes-dryingtumbler, Cylinder 5 is prefer ably provided with a plurality of compartments to which access may be had by means of a corresponding number of slidable or otherwise movable doors designated respectively by the numerals 8 and I. In practice the cylinder 5 is mount- 5 ed within and enclosed by a suitable housing or casing (not shown) ,-said casing being of known construction and having appurtenant parts to provide for initially supplying to the cylinder a flow of heated air and for thereafter supplying to 10 said cylinder a flow of air at normal or atmospheric temperature. The aforementioned casing is likewise preferably provided with a movable door or doors with which the respective compartment doors of the cylinder may be brought into register to provide for depositing'of clothes within or removal thereof from said compartments.

Cylinder 5 is adapted to be driven, through suitable speed-reducing gearing 8, by an electric motor M the armature of which is designated by the numeral 9,-said motor being provided with a series field l0 and a shunt field H. Motor M may be and preferably is of relatively small capacity, say 3 H. P. Cylinder 5 preferably has associated therewith a manually operable brake I! to provide for final stopping of the cylinder with the compartment doors thereof in register with the aforementioned casing door. I further preferably provide a worm l3 which is movable at willinto engagement with a gear I associated with the cylinder,said worm being provided with a crank handle ii to provide for manual movement of the cylinder in either direction to bring the compartment doors thereof into the desired angular position, in the event that the same are inaccurately positioned upon stopping of the cylinder by application of brake i2.

' Motor M is provided with means, including a drum i6 and associated resistance sections l1, l8 and Is, to normally provide for periodic reversal 40 and step-by-step acceleration of said motor, after completion of the circuit for the latter. Drum i6 is rotatable unidirectionally, as indi cated by the arrow,-tl 1e same being driven, through the medium of speed-reducing gearing 20, by a motor M the armature of which is designated by the numeral 2|.

Motor M is preferably of relatively large capacity, say 15 H. P., to provide for driving of the fan shown diagrammatically at 22. Motor M is provided with a series field 23 and a shunt field 24, and said motor is adapted to be connected across a suitable source of energy supply, represented by lines L L upon closure of the normally open contacts 25 of an electromagnetically operable switch 25, the operating winding of which is designated by the numeral assuming prior closure of a knife switch of usual form, as represented by the contacts 26 and 21.

Energization and de-energization of the winding 25* may be eil'ected at will through the medium oi'a pair of push-button switches 28 and 29,switch 28 being of the normally open type, and switch 29 being of the normally closed type. Thus upon closure of switch 28 a circuit is com pleted from line L by conductor 30 through said winding 2!: and through the contacts of switches 29 and 28 to line L. Switch 25, is provided with normally open auxiliary contacts 25 adapted upon closure thereof to provide a maintaining circuit for winding 25 in shunt to the push-button switch 28, as will be obvious, wherefore only momentary closure 0! the latter is necessary. Closure of switch 25 in the manner just described provides for completion of a circuit for unidirectional operation or motor M said circuit extending from line L through the series field 23 and armature 2|, thence through a starting-resistance 3| and contacts 25 to line L. the shunt field 24 extends from line L through said shunt field and contacts 25 to line L'-, as will be apparent.

Drum I6 is provided with segments 32 to 45, inclusive, and with contacts 46 to 54, inclusive, for

cooperation therewith. In the event that drum I8 is so positioned upon closure of the contacts 25'- of switch 25 as to provide for engagement of either of the segments 32 or 39 with contact 46 it will be apparent that all of the resistance sections i'l, l8 and i9 will be excluded from the armature circuit of motor M. Accordingly, to insure proper protection for motor M during starting thereof I provide for initial inclusion of resistance 3| in circuit in series with field l0 and armature 9 or said motor. Under these conditions a circuit is provided for motor M which may be traced from line L through series field "I to contact 54, segments 38 and 31 to contact 53, by conductor 55 through armature 8, conductor 58 to contact 50, thence through segments and 32 to contact 46, by conductors 51 and 58 through resistance 3|, and through the contacts 25 to line U. The circuit for shunt field H extends trom line L through-said field I and contacts 25' to line L.

I provide means for automatically excluding resistance 3| to efl'ect acceleration of motor M Said means comprises an electromagnetically operable switch 59 having normally open contacts 59 and an operating winding 59 As shown the winding 59 is connected across the terminals or armature 2|, and said winding is calibrated in a well known manner to respond and effect closure oi the contacts 59' upon attainment of predetermined current conditions in the circuit of motor M thereby short-circuiting resistance of resistance 3| to effect full speed operation of motor M I The aforedescribed automatic operation will likewise eilect exclusion of resistance 3| from the circuit of motor M, but in the meantime drum IE will have been rotated by motor M to such an extent as toprovide for proper control of the acceleration of motor M through the medium oi resistance sections l1, l8 and I9.

As will be apparent to those skilled in the art, it the drum I5 is in neutral or circuit interrupting position at the time of closure or contacts 25, the circuit for motor M will only be completed upon engagement of segments 35 to 38 The circuit forrangement may be utilized to lock or positively (or 42 to 45) with their cooperating contacts, thus initially including in the circuit of said motor both the resistance sections IT, IS and i9 and resistance M -which arrangement is not objectionable, because the motor M will under these conditions be able to start. As soon as motor M has been brought up to full speed by exclusion of resistance 3|, motor M will be subject to normal reversing and acceleration control by drum IS, the operation 01' which is believed to be obvious.

As will be apparent from the foregoing description the operation of both ofthe motors M and M is initiated simultaneously or substantially simultaneously by momentarily depressing thel push-button switch 28 In a like manner the circuits of both motors M and M may be interrupted by momentarily depressing push-button switch 29, whereby the winding 2.": is de-energized with consequent opening of the contacts 25.

Both motors M and M may be allowed to coast to a dead-stop, and if the compartment doors 6 and l of cylinder 5 do not happen to stop in registering relation to the casing door aforementioned, such registration may be effected manually by engaging worm I3 with pinion or gear H and thereafter turning or rotating the worm by means of crank handle 5. In actual practice, however, I prefer to employ a manually operable brake i2 which may be utilized to minimize the time required for stopping of motor M, and to finally effect stopping thereof with the compartment doors properly registered with the casing door. If for any reason such registration is not efiected by manipulation of brake l2, the worm and pinion means aforedescribed may be utilized to effect final angular positioning of the cylinder 5. Moreover, the worm and pinion arhold the cylinder 5 in the desired position thereof during unloading and loading of the cylinder compartments.

What I claim as new and desire to secure by Letters Patent is:

1. In a control system of the character described, in combination, a pair of electric motors, common means operable to simultaneously connect said motors across a suitable source of energy supply, means comprising resistance to be initially included in circuit with said motors jointly, means responsive to given current conditions in the circuit of one of said motors to effect exclusion of said resistance and thereby tending to simultaneously increase the speeds of both of said motors, and means including additional resistance to be included in circuit with the other of said motors individually to provide for acceleration control of the latter upon exclusion 01 said first mentioned resistance.

2. In a control system of the character described, in combination, a pair of electric motors, common means operable to simultaneously connect said motors across a suitable source of energy supply, means comprising resistance'to be 6 initiallyincluded in circuit with said motors jointly, means responsive to given current conditions in the circuit of one of said motors to eil'ect exclusion of said resistance and thereby tending to simultaneously increase the speeds of both of said motors, and means including additional resistance to be included in circuit with the other of said motors individually and to be excluded from said circuit in steps to provide for accelera- 7 tion control of the latter upon exclusion oi said first mentioned resistance.

3. In a control system of the character described, in combination, a pair of electric motors, common means operable to simultaneously connect said motors across a suitable source of energy supply, means comprising a resistance element to be initially included in circuit with said motors jointly, means responsive to given current conditions in the circuit of one of said motors to efiect exclusion of said resistance element and thereby tending to simultaneously increase the speeds of both of said motors, and means including additional resistance to be included in circuit with the other of said motors individually and to be excluded from said circuit in steps to provide for acceleration control of the latter upon exclusion of said first mentioned resistance element, said last mentioned means including means for automatically eiiecting periodic reversal of operation of said last mentioned motor. a

4. In a control system of the character described, in combination, an electric motor to be connected across a suitable source of energy supply to provide for unidirectional operation thereof, a resistance element to be initially included in circuitwith said motor to limit the value of energy supplied thereto, means operable automatically in response to given current conditions in said motor circuit to efiect exclusion of said resistance element whereby said motor is accelerated, a second electric motor to be connected across said source of energy supply, reversing and accelerating control means for said second mentioned motor, said means including a drum arranged to be driven by said first mentioned motor, a plurality of resistance sections to be controlled by said drum. and associated means to likewise insure initial inclusion of said first mentioned resistance in circuit with said second mentioned motor.

5. In a control system of the character described, in combination, an electric motor to be connected amoss a suitable source of energy supply to provde for unidirectional operation thereof, a resisuancc element to be initially included in circuit with said motor to limit the value of energy supplied thereto, means operable automatically in response to given current conditions in said motor circuit to eflfect exclusion of said resistance element whereby said motor is accelerated, a second electricmotor to be connected across said source of energy supply. reversing and accelerating control means, (or said second mentioned motor. said means including a drum arranged to be driven by said first mentioned motor, a plurality of resistance sections to be controlled by said drum, associated means to likewise insure initial inclusion of said first mentioned'resistance in circuit with said second mentioned motor, and said drum and said resistance sections cooperating to efi'ect acceleration control of said second mentioned motor independently of said first mentioned motor after exclusion of said first mentioned resistance.

6. The combination with a drying tumbler including a rotatable container, of an electric motor having a driving connection with said container, control means for said motor including a rotatable drum and a plurality of associated resistance sections, said drum being normally operable to sequentially provide reverse circuit connections for said motor and the same cooperating with said resistance sections to provide for acceleration of said motor, a tan adapted to supply a flow of fiuid to said container. a second electric motor having a driving connection with said fan,

operation of said second motor, a normally open manually operable switch adapted upon closure thereof to effect energization and closure of said switch first mentioned, said second motor having a resistance element initially included in the circuit thereof, said first motor also having connections to insure initial inclusion of said resistance element in circuit therewith, means responsive to predetermined current conditions in the circuit of said second motor to effect exclusion of said resistance element whereby said second motor is accelerated. and said drum and said resistance sections acting under the lastmentioned conditions to effect acceleration control of said first motor independently of said resistance element. 7. The combination with a drying tumbler comprising a rotatable container and a fan for supplying a fiow of air to said container, of a relatively large unidlrectionally operable electric motor having a driving connection with said fan, a relatively small reversible electric motor having a driving connection with said container, means for effecting periodic reversal and acceleration control of said relatively small motor, said means comprising a pilot drum and a plurality of resistance sections associated therewith, said relatively large motor having a driving connection with said drum, a starting resistance element to be included in the armature circuit of said relatively large motor, means for likewise initially including said resistance element in the armature circuit of said relatively small motor, a normally open electromagnetically operable switch adapted when closed to provide for substantially simultaneous completion of the armature circuits of both of said motors, a pair of push button switches respectively adapted to provide for encrgization'and de-energization of said switch at will, and means responsive to given current conditions in the armature circuit of said relatively large motor to effect exclusion of said resistance element, whereupon said drum and associated resistance sections are adapted to function in the usual manner to effect periodic reversal and acceleration control of said relatively small motor.

8. The combination with a drying tumbler comprising a rotatable container and a fan for supplying a iiow of air to said container, of a unidirectionally operable electric motor having a driving connection with said fan, a reversible electric motor having a driving connection with said container, a normally open electromagnetically operable switch adapted when closed to complete a circuit for said first mentioned motor, means including a resistance element to be initially included in circuit in series with the armature of said first mentioned motor, means including a unidirectionally operable drum and a plurality of resistance sections which cooperate to provide for periodic reversal and acceleration control of said second mentioned motor, said first mentioned motor having a driving connection with said drum, said drum and said resistance sections being so arranged as to insure initial inclusion of said first mentioned resistance in cir cuit in series with the armature of said second mentioned motor to provide for protection of the latter during starting, means including a second normally open eiectromagneticaliy operable switch having an operating winding connected across the armature of said first mentioned motor,

. said winding being operable under given current conditions to effect closure of said switch whereby said resistance element is short-circuited. and manually operable means to provide for energi zation and de-energization of said first mentioned electromagneticaily operable switch at will. 

